LTM4630IV View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTM4630IV

Dual 18A or Single 36A DC/DC µModule Regulator

Linear Technology 

LTM4630

APPLICATIONS INFORMATION

Converting the Kelvin scale to Celsius is simply taking the

Kelvin temp and subtracting 273 from it.

A typical forward voltage is given in the electrical charac-

teristics section of the data sheet, and Figure 6 is the plot

of this forward voltage. Measure this forward voltage at

27°C to establish a reference point. Then using the above

expression while measuring the forward voltage over

temperature will provide a general temperature monitor.

Connect a resistor between TEMP and VIN to set the cur-

rent to 100µA. See Figure 24 for an example.

0.8

ID = 100µA

0.7

0.6

0.5

0.4

0.3

–50 –25

0 25 50 75 100 125

TEMPERATURE (°C)

4630 F08

Figure 8. Diode Voltage VD vs Temperature T(K)

for Different Bias Currents

Thermal Considerations and Output Current Derating

The thermal resistances reported in the Pin Configuration

section of the data sheet are consistent with those param-

eters defined by JESD51-9 and are intended for use with

finite element analysis (FEA) software modeling tools that

leverage the outcome of thermal modeling, simulation,

and correlation to hardware evaluation performed on a

µModule package mounted to a hardware test board—also

defined by JESD51-9 (“Test Boards for Area Array Surface

Mount Package Thermal Measurements”). The motivation

for providing these thermal coefficients is found in JESD

51-12 (“Guidelines for Reporting and Using Electronic

Package Thermal Information”).

Many designers may opt to use laboratory equipment

and a test vehicle such as the demo board to anticipate

the µModule regulator’s thermal performance in their ap-

plication at various electrical and environmental operating

conditions to compliment any FEA activities. Without FEA

software, the thermal resistances reported in the Pin Con-

figuration section are in-and-of themselves not relevant to

providing guidance of thermal performance; instead, the

derating curves provided in the data sheet can be used in

a manner that yields insight and guidance pertaining to

one’s application-usage, and can be adapted to correlate

thermal performance to one’s own application.

The Pin Configuration section typically gives four thermal

coefficients explicitly defined in JESD 51-12; these coef-

ficients are quoted or paraphrased below:

1. θJA, the thermal resistance from junction to ambient, is

the natural convection junction-to-ambient air thermal

resistance measured in a one cubic foot sealed enclo-

sure. This environment is sometimes referred to as “still

air” although natural convection causes the air to move.

This value is determined with the part mounted to a

JESD 51-9 defined test board, which does not reflect

an actual application or viable operating condition.

2. θJCbottom, the thermal resistance from junction to the

bottom of the product case, is the junction-to-board

thermal resistance with all of the component power

dissipation flowing through the bottom of the package.

In the typical µModule, the bulk of the heat flows out

the bottom of the package, but there is always heat

flow out into the ambient environment. As a result, this

thermal resistance value may be useful for comparing

packages but the test conditions don’t generally match

the user’s application.

3. θJCTOP, the thermal resistance from junction to top of

the product case, is determined with nearly all of the

component power dissipation flowing through the top

of the package. As the electrical connections of the

typical µModule are on the bottom of the package, it

is rare for an application to operate such that most of

the heat flows from the junction to the top of the part.

As in the case of θJCBOTTOM, this value may be useful

for comparing packages but the test conditions don’t

generally match the user’s application.

For more information www.linear.com/LTM4630

4630fa

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